12AU7-6CG7 Headphone amplifier

The amplification is around 25dB with the 6CG7 valves, but you can also 6FQ7 for a little higher amplification. The downside of this is however that 6FQ7 doesn't have an electrostatic screen in the valve design. This can result in some minor audible background noise.

The impedance range of the headsets you may use starts from 50 Ohms - 500 Ohms.